Does it matter what plug it is if you're going the manual mirror way? Jaguar used both plug/socket types(whatever was in stock at the time) and you can happily wire in 3 pin mirror into 4 pin socket and the other way as well. The fourth extra wire(purple) is for dimming wing mirrors which you don't have. On my car I had the 4 pin socket(even though I have standard wing mirrors) and the Citroen mirror was 3 pin. I just wired it up directly using some breadboard wires.

 

Wiring information between 3 and 4 wire in this thread :

See Al_Roethlisberger's reference to a Honda Acura substation in post # 4

https://www.jaguarforums.com/forum/x...mirror-175709/